1. Field
The present invention relates generally to communications, and, more specifically, to a method and apparatus for providing authenticated challenges for broadcast-multicast services (BCMCS) in a wireless communication system.
2. Description
In a wireless communication system that carries non-voice traffic, such as video, data, multimedia, or other types of traffic in addition to voice traffic, a typical cellular base station may broadcast a multimedia traffic service to a plurality of mobile stations within the coverage area of the base station. The multimedia traffic service may include any number of information services similar to a number of channels included in a cable television service plan, for example. These information services typically rely upon security to maintain accountability, fairness, accuracy, confidentiality, and operability. Encryption, or the general field of cryptography, is used in electronic commerce, wireless communications, and broadcasting. In electronic commerce, encryption is used to prevent fraud and verify financial transactions. In data processing systems, encryption is used to verify a participant's identity. In broadcast-multicast service, security is maintained based on the broadcast-multicast service (BCMCS) key hierarchy. Content is encrypted with a short term key (SK) and is sent over the air. A long-term encryption key, often referred to as a broadcast access key (BAK), is provisioned into a memory module referred to as a user identification module (UIM) or universal integrated circuit card (UICC) of the mobile station. The user may be charged for the long-term encryption key BAK. The short-term key SK is derived from the BAK and a random number referred to as SKRAND. The UIM uses the BAK and the SKRAND to compute the short-term key SK. Once the UIM computes the SK, it is sent to the mobile station and the mobile station uses the SK to decrypt and view the information content. Typically, information content charging based on this method charges the user upon receipt of the BAK. Thus, the user is charged whether or not the user actually views the broadcast content. Unlike cable television, in a wireless communication system, it is desired that the actual view time of information services by a user be maintained. This is to ensure accurate billing for the content viewed and to ensure that unauthorized users, such as under-age users, for example, cannot access certain types of content. Methods that require the mobile station to register periodically or on demand have been proposed to maintain a record of actual view time by the user.
The registration message contains a list of channels the user is watching or is capable of watching. The list is used to charge the user for information services.
Typically, the methods requiring the user to register periodically or on demand are prone to theft-of-service because the mobile station may continue to receive the broadcast content without registering again in the system, thus obtaining free access to the content. In addition, an unauthorized user, such as an under-age user, for example, may access content that is prohibited by regulatory statute. Other proposed methods introduce additional encryption keys necessary to view the content of the information services. These methods suffer from a severe decrease in data-carrying capacity of the wireless system caused by the increase in overhead messages required for encryption key management.
The present invention is directed to overcoming, or at least reducing the effects of, one or more problems provided above.